Secondary battery

ABSTRACT

A secondary battery includes: an electrode assembly including a negative electrode plate, a positive electrode plate, and a separator between the negative electrode plate and the positive electrode plate; and a case accommodating the electrode assembly. The electrode assembly includes an adhesive part on an outermost region of the electrode assembly. The adhesive part is arranged to cover a boundary line between the negative electrode plate and the separator or between the positive electrode plate and the separator, and is bonded to the case.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2020-0132206, filed on Oct. 13, 2020 in the KoreanIntellectual Property Office, the entire disclosure of which isincorporated herein by reference.

BACKGROUND 1. Field

Aspects of embodiments of the present invention relate to a secondarybattery.

2. Description of the Related Art

Secondary batteries each include: an electrode assembly that includes apositive electrode, a negative electrode, a separator interposed betweenthe positive electrode and the negative electrode; and a case thataccommodates the electrode assembly with an electrolyte. The electrodeassembly is provided as a structure in which a plurality of electrodeassemblies are stacked. Also, the electrode assembly is provided as aroll form in which an electrode assembly is wound in a direction, andthis is typically referred to as a jelly roll.

In the electrode assembly, a binder is used to fix the positiveelectrode, the negative electrode, and the separator so as to maintain astate in which the positive electrode, the negative electrode, and theseparator are stacked. Also, a plurality of protective tapes may be usedto reduce damage due to impact when the secondary battery is dropped.

However, edge portions of the electrode assembly, which are not coatedwith the binder, are vulnerable to impact when dropped. Thus, theelectrode assembly may be damaged due to curling or tearing of theseparator.

The above information disclosed in this section of “Description of theRelated Art” is provided for enhancement of understanding of thebackground of the present invention, and therefore it may containinformation that does not form the related art.

SUMMARY

According to an aspect of embodiments of the present invention, asecondary battery in which an electrode assembly has an improved bindingstructure, thereby minimizing or reducing damage of the electrodeassembly (e.g., a jelly roll) due to dropping impact, is provided.

According to one or more embodiments, a secondary battery includes: anelectrode assembly including a negative electrode plate, a positiveelectrode plate, and a separator between the negative electrode plateand the positive electrode plate; and a case configured to accommodatethe electrode assembly, wherein the electrode assembly includes anadhesive part on an outermost region of the electrode assembly, whereinthe adhesive part is provided to cover a boundary line between thenegative electrode plate and the separator or between the positiveelectrode plate and the separator, and is bonded to the case.

The electrode assembly may include: a first surface and a secondsurface, which are positioned at outermost regions of the electrodeassembly and face away from each other; and a third surface and a fourthsurface, which have smaller areas than the first surface and the secondsurface and connect the first surface to the second surface, wherein theadhesive part is on either the first surface or the second surface or onboth the first surface and the second surface.

The adhesive part may cover a region of about 20% to about 100% of alength (L2) which is from the boundary line (L1) between the negativeelectrode plate and the separator or between the positive electrodeplate and the separator to an end of the separator.

The case may include: a recess which is an accommodation spaceconfigured to accommodate the electrode assembly; and a sealing portionat an outer circumferential edge of the recess and sealed after theelectrode assembly is accommodated, wherein the case has a surface thatfaces the adhesive part.

An area of the adhesive part may be about 30% or more of an area of thefirst surface or the second surface.

A thickness of the adhesive part may be about 1 μm to about 50 μm.

The electrode assembly may further include a tape which is attached toan end on the adhesive part adjacent to the boundary line (L1) betweenthe negative electrode plate and the separator or between the positiveelectrode plate and the separator.

According to one or more embodiments, a secondary battery includes: anelectrode assembly including a first electrode plate, a second electrodeplate, and a separator between the first electrode plate and the secondelectrode plate; a case configured to accommodate the electrodeassembly; and an adhesive part on an outermost region of the electrodeassembly, wherein the adhesive part is adjacent to an end of theseparator beyond a boundary line (L1) between the separator and thefirst or second electrode plate, and is bonded to the case in a state inwhich the electrode assembly is accommodated in the case.

The electrode assembly may include: a first surface and a secondsurface, which are positioned at outermost regions of the electrodeassembly and face away from each other; and a third surface and a fourthsurface, which have relatively smaller areas than the first surface andthe second surface and connect the first surface to the second surface,wherein the adhesive part is on either the first surface or the secondsurface or on both the first surface and the second surface.

The adhesive part may cover a region of about 20% to about 100% of alength (L2) which is from the boundary line (L1) between the separatorand the first or second electrode plate to the end of the separator.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure, and are incorporated in andconstitute a part of this specification. The drawings illustrate someembodiments of the present disclosure and, together with thedescription, serve to explain principles of the present disclosure. Inthe drawings:

FIG. 1 is a partially exploded perspective view illustrating a secondarybattery according to an embodiment of the present disclosure;

FIG. 2 is a plan view of an electrode assembly of FIG. 1;

FIG. 3 is a schematic view illustrating a portion of the electrodeassembly of FIG. 2;

FIG. 4 is a view showing stress distribution of an electrode assemblywhen a secondary battery having a general structure is dropped; and

FIG. 5 is a view showing stress distribution of an electrode assemblywhen a secondary battery according to an embodiment of the presentdisclosure is dropped.

DETAILED DESCRIPTION

Some embodiments of the present disclosure are provided to more fullydescribe the present disclosure to those skilled in the art. Thefollowing embodiments may be modified in many different forms, and thescope of the present disclosure is not limited to the followingembodiments. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey theconcept of the present disclosure to those skilled in the art.

In the drawings, the thickness and size of components or layers may beexaggerated for convenience of explanation and clarity, and likereference numerals refer to like elements throughout. As used in thisspecification, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Also, in this specification,it is to be understood that when an element A is referred to as being“connected to” an element B, the element A may be directly connected tothe element B, or one or more intervening elements C may be presentbetween the elements A and B such that the element A may be indirectlyconnected to the element B.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting of the disclosure. Asused herein, the singular forms are intended to include the plural formsas well, unless the context clearly indicates otherwise. Also, it is tobe further understood that the terms “comprise” or “include” and/or“comprising” or “including,” when used in this specification, specifythe presence of stated features, numbers, steps, operations, members,elements, and/or groups thereof, but do not preclude the presence oraddition of one or more other features, numbers, steps, operations,members, elements, and/or groups thereof.

It is to be understood that, although the terms “first,” “second,” etc.may be used herein to describe various members, components, regions,layers, and/or portions, these members, components, regions, layers,and/or portions should not be limited by these terms. These terms areused to distinguish one member, component, region, layer, or portionfrom another member, component, region, layer, or portion. Thus, a firstmember, component, region, layer, or portion which will be described mayalso refer to a second member, component, region, layer, or portion,without departing from the teachings of the present invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. These spatially relative termsare intended for ease of comprehension of the present inventionaccording to various process states or usage states of the presentinvention, and the present invention is not limited thereto. Forexample, when an element or feature shown in the drawings is turnedupside down, the element or feature described as “beneath” or “below”may then be “above” or “upper.” Thus, the term “beneath” may encompassthe term “above” or “below.”

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the inventive concept pertains. Itis also to be understood that terms defined in commonly useddictionaries should be interpreted as having meanings consistent withthe meanings in the context of the related art, and are expresslydefined herein unless they are interpreted in an ideal or overly formalsense.

Herein, a secondary battery according to some embodiments of the presentdisclosure will be described in further detail with reference to theaccompanying drawings.

FIG. 1 is a partially exploded perspective view illustrating a secondarybattery according to an embodiment of the present disclosure; FIG. 2 isa plan view of an electrode assembly of FIG. 1; and FIG. 3 is aschematic view illustrating a portion of the electrode assembly of FIG.2.

As illustrated in FIGS. 1 to 3, a secondary battery 10 according to anembodiment of the present disclosure may include an electrode assembly100, a case 300 which has a pouch shape to accommodate the electrodeassembly 100, and an adhesive part 170 by which the electrode assembly100 is bonded to the case 300.

As illustrated in FIG. 1, the electrode assembly 100 may include anegative electrode plate 110, a positive electrode plate 130, and aseparator 150 interposed between the negative electrode plate 110 andthe positive electrode plate 130. In an embodiment, the electrodeassembly 100 may be a stack-type electrode assembly in which a stack ofthe negative electrode plate 110, the separator 150, and the positiveelectrode plate 130 is repeatedly stacked a plurality of times. Also, inan embodiment, the electrode assembly 100 may be a roll-type electrodeassembly in which a stack of the negative electrode plate 110, theseparator 150, and the positive electrode plate 130 is wound. Thiselectrode assembly 100 may be referred to as a jelly roll. In thepresent disclosure, the electrode assembly 100 will be described as anexample of the wound type.

As illustrated in FIGS. 1 and 2, the negative electrode plate 110 may beformed by applying a negative electrode active material to both surfacesof a negative electrode current collector plate which is made of, forexample, a metal foil, such as copper, a copper alloy, nickel, or anickel alloy. For example, a carbon-based material, Si, Sn, a tin oxide,a composite tin alloy, a transition metal oxide, or a lithium metalnitride or metal oxide may be used as the negative electrode activematerial. A negative electrode non-coating portion, to which thenegative electrode active material is not applied, may be formed in someregions of the negative electrode current collector plate. A negativeelectrode tab 112 may be provided on the negative electrode non-coatingportion and electrically connected to the negative electrode non-coatingportion. An insulating member 114 may be attached to the negativeelectrode tab 112 to prevent or substantially prevent a short circuitbetween the negative electrode tab 112 and the case 300. In anembodiment, the negative electrode plate 110 may be relatively longerthan the positive electrode plate 130 with respect to the longitudinaldirection, as illustrated in FIG. 3.

As illustrated in FIGS. 1 and 2, the positive electrode plate 130 may beformed by applying a positive electrode active material to both surfacesof a positive electrode current collector plate which is made of, forexample, an aluminum metal foil having excellent electricalconductivity. For example, a chalcogenide compound may be used as thepositive electrode active material. Also, as an example, a compositemetal oxide, such as LiCoO₂, LiMn₂O₄, LiNiO₂, and LiNiMnO₂, may be used.A positive electrode non-coating portion, to which the positiveelectrode active material is not applied, may be formed in some regionsof the positive electrode current collector plate. A positive electrodetab 132 may be provided on the positive electrode non-coating portionand electrically connected to the positive electrode non-coatingportion. An insulating member 134 may be attached to the positiveelectrode tab 132 to prevent or substantially prevent a short circuitbetween the positive electrode tab 132 and the case 300. In anembodiment, the positive electrode plate 130 may be relatively shorterthan the negative electrode plate 110 with respect to the longitudinaldirection, as illustrated in FIG. 3.

As illustrated in FIGS. 1 and 2, the separator 150 may be interposedbetween the negative electrode plate 110 and the positive electrodeplate 130 to prevent or substantially prevent a short circuittherebetween. The separator 150 may include, for example, a materialselected from the group consisting of polyethylene, polypropylene, and aporous copolymer of polyethylene and polypropylene. The separator 150may be formed larger than the negative electrode plate 110 and thepositive electrode plate 130 so as to prevent or substantially preventan electrical short circuit between the negative electrode plate 110 andthe positive electrode plate 130. Particularly, in an embodiment, in thelongitudinal direction of FIG. 3, the separator 150 is longer than thenegative electrode plate 110 that is relatively longer than the positiveelectrode plate 130.

The electrode assembly 100 having the above-described structure may bestacked or wound, thus providing a first surface 102 and a secondsurface 104, which face away from each other in an up-down direction ofFIG. 1, and a third surface 106 and a fourth surface 108, which connectthe first surface 102 and the second surface 104. In an embodiment, thefirst surface 102 and the second surface 104 may be relatively largerand flatter surfaces than the third surface 106 and the fourth surface108. The third surface 106 and the fourth surface 108 may be surfacescorresponding to side surfaces of the electrode assembly 100 in FIG. 1,and, in an embodiment, may be relatively narrower curved surfaces thanthe first surface 102 and the second surface 104. The first to fourthsurfaces 102 to 108 may be provided by any of the negative electrodeplate 110, the positive electrode plate 130, or the separator 150 whichis positioned at an outermost region when the electrode assembly 100 isstacked or wound. In the present disclosure, an embodiment in which theelectrode assembly 100, which is wound such that the positive electrodeplate 130 is positioned at the outermost region, will be described as anexample.

The adhesive part 170, which will be described later, may be provided onthe first surface 102 and/or the second surface 104. In portions exceptfor the first to fourth surfaces 102 to 108, multi-layer structures areexposed when stacked or wound. Thus, these portions are not referred toas separate surfaces. In an embodiment, the negative electrode tab 112and the positive electrode tab 132 protrude from one of both ends fromwhich the stacked or wound shape is exposed.

As illustrated in FIG. 1, the case 300 may be a pouch- or pocket-type.Portions of a laminate exterior material are bent so as to face eachother, and a recess 310 for accommodating the electrode assembly 100 maybe formed in the case 300 by pressing or drawing, for example. A sealingportion 330 is formed in an outer circumferential edge of the recess310, and the sealing portion 330 is sealed by heat fusion or the like ina state in which the electrode assembly 100 is accommodated in therecess 310. Some of the surfaces of the recess 310 face the firstsurface 102 or the second surface 104, and the surfaces bent and facingeach other also face the first surface 102 or the second surface 104.Thus, when the electrode assembly 100 is accommodated in the case 300,the adhesive part 170 is provided on the first surface 102 and/or thesecond surface 104. Thus, the electrode assembly 100 and the case 300may be bonded to each other.

Herein, the adhesive part 170 will be described in further detail.

As illustrated in FIGS. 2 and 3, the adhesive part 170 may be provided,for example, on either the first surface 102 or the second surface 104or on both the first surface 102 and the second surface 104. Theadhesive part 170 bonds the positive electrode plate 130 and theseparator 150 of the electrode assembly 100 together and also bonds theelectrode assembly 100 and the inner surface of the case 300 together.That is, the adhesive part 170 serves as a binder.

The adhesive part 170 may be dispensed in a dot array shape, a presseddot array shape, a solid line shape having rows and columns, a dotted ordiagonal line shape, a zigzag shape, or the like.

In an embodiment, the adhesive part 170 may include a polymer or amixture of two or more polymers selected from the group consisting ofcellulose, polyvinylidene fluoride-co-hexafluoropropylene,polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate,polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone,polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide,polyarylate, cellulose acetate, cellulose acetate butyrate, celluloseacetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol,cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methylcellulose, and polypropylene-maleic acid anhydride. Here, for example,the polybutylacrylate and polyacrylonitrile may be polar adhesives, andthe polypropylene-maleic acid anhydride may be a non-polar adhesive.

In an embodiment, when the adhesive part 170 is formed, the adhesivepart 170 may be provided to occupy at least about 30% or more of thearea of the first surface 102 and/or the second surface 104. When theformation area of the adhesive part 170 is less than about 30%, theadhesion strength between the electrode assembly 100 and the case 300may deteriorate. In an embodiment, the thickness of the adhesive part170 may be about 1 μm to about 50 μm. When the thickness of the adhesivepart 170 is less than about 1 μm, the adhesion strength between theelectrode assembly 100 and the case 300 may deteriorate. When thethickness of the adhesive part 170 is greater than about 50 μm, thesecondary battery 10 may become unnecessarily thick. However, the areaand thickness of the adhesive part 170 are not limited to the numericalvalues stated above. For example, the negative electrode plate 110 orthe positive electrode plate 130 are positioned on the outermost regionwhen the electrode assembly 100 is stacked or wound, and the adhesivepart 170 is formed thereon. In an embodiment, an adhesive is applied andthen subjected to post-processes (HPC/DF/CP, a thermal compressionprocess), and, accordingly, the thickness of the adhesive part 170 maybecome about 1 μm to about 50 μm. In an embodiment, for example, theseparator 150 is positioned on the outermost region when the electrodeassembly 100 is stacked or wound, and, then, the adhesive part 170 isformed thereon. In this case, an adhesive is applied and then subjectedto post-processes (HPC/DF/CP, a thermal compression process), and,accordingly, the thickness of the adhesive part 170 may become about 50μm or more.

Referring to FIGS. 1 and 2, it is not necessary for the adhesive part170 to cover the entire width of the first surface 102 and/or the secondsurface 104 in the width direction. That is, the adhesive part 170 maybe dispensed adjacent to the third surface 106 and the fourth surface108, or may be dispensed spaced a distance (e.g., a predetermineddistance) from the third surface 106 and the fourth surface 108. In anembodiment, the adhesive part 170 is dispensed in the longitudinaldirection of the first surface 102 and/or the second surface 104, whilehaving the area allowing the positive electrode plate 130 and theseparator 150 to be bonded to each other. That is, the adhesive part 170may be formed up to a region beyond a boundary line L1 between thepositive electrode plate 130 and the separator 150 in the longitudinaldirection of FIG. 3. For example, the boundary line between the positiveelectrode plate 130 and the separator 150 may be defined as about 0%,and an end of the separator 150 in the longitudinal direction may bedefined as about 100%. In this case, the adhesive part 170 may be formedto cover at least about 20% to about 100% of a length (defined as a“residual length L2” of the separator) from the boundary line betweenthe positive electrode plate 130 and the separator 150 to the endportion of the separator 150. For example, the residual length L2 of theseparator 150 corresponding to the range of about 20% to about 100% maybe about 0.4 mm to about 2 mm.

The separator 150 is longer than the positive electrode plate 130, and,thus, when the adhesive part 170 is formed up to the region beyond theboundary line L1 between the positive electrode plate 130 and theseparator 150, the adhesion strength between the separator 150 and thepositive electrode plate 130 may be increased. Accordingly, it ispossible to minimize or reduce curling of the separator 150, separationof the positive electrode plate 130, or the like due to impact generatedwhen the secondary battery 10 is dropped.

This will be described in further detail with reference to FIGS. 3, 4,and 5.

FIG. 4 is a view showing stress distribution of an electrode assemblywhen a secondary battery having a general structure is dropped. FIG. 5is a view showing stress distribution of an electrode assembly when asecondary battery according to an embodiment of the present disclosureis dropped.

As illustrated in FIG. 4, it may be found that the stress distribution,which is generated in an electrode assembly when a secondary battery isdropped, is concentrated on edges of the electrode assembly. The stressof about 76 MPa is concentrated in the up-down direction of FIG. 4, andthe stress of about 93 MPa is concentrated in the left-right direction.

However, the left-right direction of the electrode assembly 100corresponds to the width direction of FIG. 3, and, in this direction, aboundary surface, in which a negative electrode plate 110, a positiveelectrode plate 130, and a separator 150 are stacked or wound, is notexposed (the third surface and the fourth surface of FIG. 1). However,the up-down direction of the electrode assembly 100 corresponds to thelongitudinal direction of FIG. 3, and, in this direction, the boundarysurface, in which the negative electrode plate 110, the positiveelectrode plate 130, and the separator 150 are stacked or wound, isexposed (regions except for the first to fourth surfaces of FIG. 1).Also, the separator 150 longer than the negative electrode plate 110 andthe positive electrode plate 130 is in a state in which the end thereofis exposed. Thus, the separator 150 is vulnerable to external impactmore in the up-down direction of the electrode assembly 100 than in theleft-right direction of the electrode assembly 100.

Thus, when the adhesion strength between the electrode assembly 100 andthe case 300 is reduced or a free electrolyte is increased, movement ofthe electrode assembly 100 inside the secondary battery 10 is increased.When the secondary battery 10 is dropped, the stress generated in theleft-right direction of the electrode assembly 100 is greater than thestress generated in the up-down direction. However, the portions in theup-down direction are vulnerable to the impact, and, thus, the separator150 may be curled or separated due to even smaller stress than thestress in the left-right direction. In this case, the electrode assembly100 may move, or the positive electrode plate 130 may come into contactwith the negative electrode plate 110. Accordingly, a short circuit mayoccur. When the short circuit occurs, damage to the case 300 and leakageof the electrolyte due to heat generation, thermal runaway due toignition, or the like may occur.

However, according to embodiments of the present invention, the adhesivepart 170 is formed to be able to sufficiently cover the boundary line L1between the positive electrode plate 130 and the separator 150 and theregions of the residual length L2 as illustrated in FIG. 3. Asillustrated in FIG. 5, when the adhesive part 170 according to anembodiment of the present disclosure is applied, the stress generated inthe electrode assembly 100 when dropped is significantly reduced. Evenin the same conditions as FIG. 4, the stress generated in the up-downdirection of FIG. 5 may be reduced to about 2.3 MPa to about 5.3 MPa.Accordingly, by applying the adhesive part 170 of the presentdisclosure, it is possible to minimize or reduce curling of theseparator 150, separation of the positive electrode plate 130, or thelike due to the impact generated when the secondary battery 10 isdropped.

Meanwhile, in FIG. 3, when an upper portion is defined as the upper sideof the electrode assembly 100 in the longitudinal direction and a lowerportion is defined as the lower side in the longitudinal direction, anupper tape 180 and a lower tape 190 may be attached to the upper portionand the lower portion of the electrode assembly 100, respectively. Theupper tape 180 and the lower tape 190 may fix the adhesive part 170 andthe separator 150. The upper tape 180 and the lower tape 190 may bearranged in the middle of the adhesive part 170 in the width direction.The upper tape 180 and the lower tape 190 may facilitate maintaining thestacked or wounded state of the electrode assembly 100 when theelectrode assembly 100 is inserted into the case 300.

Generally, the electrode assembly 100 is configured such that two tapesare attached to the lower portion of the electrode assembly 100 to fixthe lower end of the electrode assembly 100. In this case, the lowertapes cover most of the lower portion of the electrode assembly 100.When the adhesive part 170 is formed under the state described above,the adhesion strength between the positive electrode plate 130 and theseparator 150 in the lower portion of the electrode assembly 100deteriorates. Thus, the effect of extending the adhesive part 170 in theup-down direction of the electrode assembly 100 may not be realized.Thus, according to an embodiment of the present disclosure, a structurein which the lower tape 190 is minimized or reduced in size is providedto perform a function of maintaining the insertability of the electrodeassembly 100. Instead, the adhesive part 170 has a function ofprotecting the electrode assembly 100 when dropped.

According to embodiments of the present disclosure as described above, astructure is provided to minimize or reduce the size of the tape thatmaintains the shape of the electrode assembly when the electrodeassembly is inserted into the case, and this structure maximizes orincreases the area of the adhesive part. Accordingly, the tape performsa function of maintaining the insertability, and the protection of theelectrode assembly when the secondary battery is dropped is performed bythe adhesive part. The formation area of the adhesive part is large toprevent or substantially prevent a short circuit due to curling of theseparator, separation of the positive electrode plate, or the like, whenthe secondary battery is dropped, thereby enhancing the safety againstdropping of the secondary battery.

According to embodiments of the present disclosure, the bonding strengthbetween the negative electrode, the separator, and the positiveelectrode within the electrode assembly is enhanced, and, thus, curlingor separating of the separator may be minimized or reduced even when animpact occurs due to dropping. Accordingly, an internal short circuit ofthe electrode assembly may be prevented or substantially prevented, and,thus, heat generation or ignition when dropped may be prevented orsubstantially prevented.

The above-described embodiments are merely provided as exampleembodiments for carrying out the present disclosure, and the presentdisclosure is not limited to the above-described embodiments, and thetechnical spirit of the present disclosure includes all ranges oftechnologies that may be variously modified by a person of ordinaryskill in the art to which the present disclosure pertains, withoutdeparting from the scope of the present disclosure as set forth in thefollowing claims.

What is claimed is:
 1. A secondary battery comprising: an electrodeassembly comprising a negative electrode plate, a positive electrodeplate, and a separator between the negative electrode plate and thepositive electrode plate; and a case configured to accommodate theelectrode assembly, wherein the electrode assembly comprises an adhesivepart on an outermost region of the electrode assembly, wherein theadhesive part is arranged to cover a boundary line between the negativeelectrode plate and the separator or between the positive electrodeplate and the separator, and is bonded to the case.
 2. The secondarybattery of claim 1, wherein the electrode assembly comprises: a firstsurface and a second surface, which are positioned at outermost regionsof the electrode assembly and face away from each other; and a thirdsurface and a fourth surface, which have smaller areas than the firstsurface and the second surface and connect the first surface to thesecond surface, wherein the adhesive part is on at least one of thefirst surface and the second surface.
 3. The secondary battery of claim2, wherein the adhesive part covers a region of 20% to 100% of a lengthwhich is from the boundary line between the negative electrode plate andthe separator or between the positive electrode plate and the separatorto an end of the separator.
 4. The secondary battery of claim 3, whereinan area of the adhesive part is 30% or more of an area of the firstsurface or the second surface.
 5. The secondary battery of claim 3,wherein a thickness of the adhesive part is 1 μm to about 50 μm.
 6. Thesecondary battery of claim 3, wherein the electrode assembly furthercomprises a tape which is attached to an end on the adhesive partadjacent to the boundary line between the negative electrode plate andthe separator or between the positive electrode plate and the separator.7. The secondary battery of claim 2, wherein the case comprises: arecess which is an accommodation space configured to accommodate theelectrode assembly; and a sealing portion which is at an outercircumferential edge of the recess and sealed after the electrodeassembly is accommodated, wherein the case has a surface that faces theadhesive part.
 8. A secondary battery comprising: an electrode assemblycomprising a first electrode plate, a second electrode plate, and aseparator between the first electrode plate and the second electrodeplate; a case configured to accommodate the electrode assembly; and anadhesive part on an outermost region of the electrode assembly, whereinthe adhesive part is adjacent to an end of the separator beyond aboundary line between the separator and the first or second electrodeplate, and is bonded to the case in a state in which the electrodeassembly is accommodated in the case.
 9. The secondary battery of claim8, wherein the electrode assembly comprises: a first surface and asecond surface positioned in outermost regions of the electrode assemblyand facing away from each other; and a third surface and a fourthsurface, which have smaller areas than the first surface and the secondsurface and connect the first surface to the second surface, wherein theadhesive part is on at least one of the first surface and the secondsurface.
 10. The secondary battery of claim 9, wherein the adhesive partcovers a region of 20% to 100% of a length which is from the boundaryline between the separator and the first or second electrode plate tothe end of the separator.